No. An STC is not applicable to an Experimental. There is no type certificate to begin with.
The STC, which incorporates by reference the related TC, approves not only the modification but also how that modification affects the original design.
https://www.faa.gov/aircraft/air_cert/design_approvals/stc
A special airworthiness certificate in the experimental category is issued to operate an aircraft that does not have a type certificate or does not conform to its type certificate and is in a condition for safe operation.
https://www.faa.gov/aircraft/air_cert/airworthiness_certification/sp_awcert/experiment